Five years of support are requested to study the aging pituitary ovarian axis. We seek to understand pituitary-ovarian communication via follicle-stimulating hormone (FSH). It is well known that in women over the age of 35 fertility declines compared with younger women. Infertility clinics report decreased responsiveness of older women to exogenous FSH preparations. This project will focus on the response of the aging ovary to a change in relative abundance of two major human (h) FSH glycoforms. The classic hFSH possessing both alpha subunit and beta subunit oligosaccharides is designated tetra-glycosylated hFSH and a novel hFSH glycoform possessing only alpha subunit oligosaccharides is designated di-glycosylated hFSH. Women aged 21-24 express more di-glycosylated hFSH than tetra-glycosylated hFSH, perimenopausal women express slightly less di-glycosylated hFSH, while post-menopausal women express primarily tetra-glycosylated hFSH. Project 1 will investigate the changes in relative abundance of hFSH glycoforms during the menstrual cycle that are associated with increasing age and study mechanisms for glycan modulation of FSH receptor binding and activation. Project 2 will compare the activities of hFSH glycoforms in a variety of signal transduction assays in the ovary in order to identify possible mechanisms that enhance the biological activity of di-glycosylated hFSH. The differential effects of both glycoforms on bone resorption will also be studied. Project 3 will create mouse models to test the hypothesis that both hFSH glycoforms are necessary for reproductive function. A double hFSH glycosylation mutant will replace the normal mFSH gene. This line will be crossed with FSH null mice to see if it can rescue female infertility. Purified hFSH glycoforms will also be tested in vivo using FSH null mice. The WSU FSH process core laboratory (Core B) will provide well characterized purified hFSH glycoforms, to all projects. The initial products will be di-glycosylated hFSH and tetra-glycosylated hFSH, which are of interest to all the scientific projects, but are not available from other sources. Recombinant di-glycosylated hFSH will be expressed first, due to low abundance in natural sources. Core B will characterize glycan populatlons at each occupied N-glycosylation site, thereby providing fully characterized glycoforms with known, rather than assumed glycosylation differences. Core B will also provide cell culture and assay services to project investigators. The WSU bioinformatics core (Core C) will provide a data-sharing platform readily accessible to all investigators via the internet. The outcome of this research will be a better understanding of the mechanisms for reduced ovarian responsiveness with aging that may lead to the development of more effective FSH preparations for treating infertility. While currently available preparations work well in young women, they become increasingly ineffective in older women, requiring higher doses and prolonged administration yet producing fewer oocytes.